Directive radio repeating system



L. EsPENscHn-:D E1' AL DIRECTIVE RADIO REPEATING SYSTEM MuyA s, 192s.1,668,631

Filed Dc. 28, 1921 4 Sheets-Sheet 1 May 8, 1928. 1,668,637

K L. ESPENSCHIED ET AL DIRECTIVE RADIO REPEATING SYSTEM Filed Deo, 28,1921 4 Sheets-Sheet 2 7 X2 /s j; f ii 72 l; f5, Y lm-wlw@ @Q j l 56p kllllli -Il iIll l j ATTORNEY my s, xsi-2a l.. 4EsF'rsNscHlr-:D ET Al.

-DIRECTIVE RADIO REPEATING SYSTEM Filed DfQzs, 1921 4 Sheets-Sheet 3INVENTQRS ATTORNEY May 8, 1928.

L. ESPENSCHIED ET AL DIRECTIVE RADIO REPEATING SYSTEM Filed Dec. 28,1921 4 Sheets-Sheet 4 ATTORNEY Patented May 8,1928.

UNITEDSTATES 1,668,637 Pari-:rrrA ori-icaN LLOYD ESPENSCHIED, orQUEENs-NEWYORK, AND nnnoss K. MARTIN, oF ORANGE, NEW JERSEY, AssIGNoRsTo `AixerriucAN TELEPHONE AND TELEGRAPH COMPANY,

A CORPORATION OF VNEIN'` YORK.

DIRECTIVE RADIO REPEATINGSYSTEM.

App1icaton-1led Decemberi28, 1921. `Serial No. 525,440.

This Vinventionrelates to directive radio repeating systems `andparticularlyr `to that type ofsystem adjusted to have abilateralreceiving and transmitting characteristic 5 and in which transmissionand reception oc` cur at the same frequency.`

The radio repeating systems heretofore designed comprise a singleantenna and an amplifying circuit connected therewith which were`adapted to amplify Vwaves received from any direction and transmit theamplified waves in all directions. `N ot only were thesesystemsineilicient because of the lack of a directional characteristicin receiving` and sending but also the degree of amplification wassomewhaty low, being limited by the tendencyV of the repeater to sing.

One of the objects of this invention'is to provide a repeater systemhaving controllable directivity, and balanced so that greatamplification can be obtained without producing singing in the repeatercircuit and thereby rendering it inefficient. i Another object of thisinvention to pro` ride a system suitable for long distance signaling inwhich the effects of static are minimized by the use of short waves,which, as is well known, are less affected by static than are longwaves. Furthermore, the effect of static maybe minimized by sustainingthroughout the course of transmission the ratio of the signaling energyto static, which result may be attained by spacing the directiverepeating stations at certain predetermined points, depending upon thedrop in the energy level between the successive repeating stations. i

By the use of repeating stations embody-` ing directive antenna arrayssuch, for eX- ample, as aredescribed in the copending application of G.A. CampbelLSerial No. 327,- 553. filed September 30, 1919, and properlydesigned and adjusted amplifying circuits, the course of transmission1of signals between widely separated terminals may be controlled, sinceit is practicable, by` properly locating the repeating stations, todirect the transmission either along a straight line between the twoterminals, or along a more devious course. This `feature of ourinvention becomes important when it is de- ,sired to avoid objects lyingbetween the two terminals which would tend to interfere with formerbeing characterized by a verticalA antenna array and the latter by aloop an` tenna. array; Fig.V 3 shows a alanced arrangementl usinghorizontal and Vertical antennae: Fig. 4 shows an arrangement usinghorizontal and vertical antennae adapted for duplex operation; Fig. 4shows the radiation characteristic of the arrangements shown in theforegoing figures and Fig. 4b is a. frequency chart of Fig. 4; Fig. 5shows an arrangement for receiving by a loop antenna andtransmitting bya vert-ical antenna, the characteristic of the loop antenna being shownin Fig. 5a; Figs. 6 and 6a show other forms of circuits similar to Fig.5, but adapted for the duplex operation; Fig. 7 shows a circuit havingseparate receiving and transmitting antenn and characterized b v aconnecting circuit between the transmitting and receiving antennae toprevent interference between them; Figs. 8 and 9 show completeradio`systems embodying a directive repeater for relaying the signalsbetweenthe terminal stations, Fig.` 9 being distinguished from Fig. 8 bythe use of a single source of carrier oscillations for modn` lation anddemodulation at both terminals; and Fig. l() shows a method forarranging repeater stations to prevent singing between adjacent ones.

In Fig. l, X1, X2 and X, represent three antennae of an array, which arespaced a definite part of a wave length apart. Each antenna hasconnected theretoan amplifymg circuit having a phase shifting device theinput side of the amplifying circuit, and a power amplifier A2, a bandfilter F1 and a phase shifting device PS2 inthe output side of the saidcircuit. The antenna X, is connected with the amplifying circuitbyymeans of the multi-winding transformer T, with which is alsoconnected a network N, designed to balance the antenna X1. The an* `FS1a band filter F1 and an amplifier A, in

tennae X2 and X3 are connected with amplifying circuits similar to thatshown in connection with the antenna Xl. Y

Oscillations set up in the antennae as the result of anelectromagneticwave will beimpressed'by the transformers upon the input side of theamplifying circuits. Thus, for example, oscillations set up in antennaXl will be impressed by the transformer T1 upon the amplifying circuit.The phase of the current will be changed by the phase shift-ing devicePS., and the current will then pass through the band filter F1, which ispreferably designed to transmit a band of frequencies represented by thecarrier frequency plus the signaling frequency er the carrier frequencyminus the signaling frequency. The currentl traversing the band ilterwill be amplified, liistby the low power amplifier A, .and then by thehigh power amplifier A2. The resultant current will be transmittedthrough the band filter F2 having the same characteristic as the filterFl. The phase shifting device PS.I is designed to control the phase ofthe current applied tothe antenna Xl for transmission therefrom. Byproperly spacing the antenna constituting the array and by the propercontrol of the amplitude and the phase of the currents applied lto theindividual antenna of the array according to the principles set vforthin thecopending application to G. A. Campbell, Serial No. 827,553, filedSeptember 30,1919, ive may obtain, for example, the bilateral radiationlcharacteristic shown in Fig. eta. This characteristic indicates maximumreceiving and transmiting efficiency along the axis of thecharacteristic, which is perpendicular to the axis of the array. It willaccordingly be seen that by means of the repeater arrangement shown inFig. l, adjusted so as to have the characteristic shown in Fig. Il", itis practicable to receive signals from both directions perpendicular tothe axis of the array and to transmit amplified signals in bothdirections from the axis of the array. The frequencies of the receivedsignals depend, of course, upon the timing of the autenn and also uponthe frequency range of the band filters. Since reception andtrancmission are effected on the same frequency, it is necessary tobalance theindividua'l vantennae by means of a balancingnetivork such asN1 shoivn in connection with the Xl in order to prevent the continuouscirculation of energy Within the repeater circuit, known as singing.

The arrangement shown in Fig. .2 is in generalsimilar to thatshown inFig. 1, excepting that loop antennae take the place of the verticalantennae shown in Fig. 1. The characteristic of loop antenna, shown inFig. 5, indicates maximum reception and transmission of energyT along anaxis lying within the plane of each antenna constituting the array. Theloops aie adjusted for the reception and transmission of signalsof thesame fre uency. The current setup in the loop by tie high frequency WaveWill beimpressed upon the input branch of the amplifying circuit passingthrough the phase shifter PS1, the band filter F1, and low poweramplifier A, then through the high power amplifier A2, a second bandfilterFg and a second phase shifter PS2, which controls the phase of thecurrent applied through the transformer Tj to the loop antenna. Byproper spacing of the loops and by proper control of the amplitude andphase of the current applied to each antenna, of the array, thedirection of reception and transmission of signals may be controlled.The advantage of using the loop array is that the same degree ofdirective transmission or reception may be obtained with fewer unitsthan with the vertical array. Since transmission and lrecept-ion areeffected by the same carrier frequency, singing is prevented by theproper balancing of the loops by the networks Nas shown in the ligure.

1ig. 3 shoivs a repeater, adjusted for re ceiving and transmitting uponthe same fre quency, in which signalsy are received by a horizontalantenna which is balanced with respect to the vertical antenna whichtransmits the amplified signals. 4Tn tliisarrangement each unitlcomprises ahoriaontai antenna, a vertical antenna and an amplifyingcircuit. Although in the figure the vertical and horizontal antennae ofeach unit are shown in close proximity to each ,ilher,

and the arious units are spaced at delinif.: fractions of a Wave length.apart, itis desiicd to point out that all of the vertical :iiiteiineemaybe arrangeril in a group, ear-h located at the proper distance fromthe others, and similarly all of the liorh/.ontal antenna may be groupedtogether. euch located at the proper distance from the others. This nocefates, however, that the rei-pective amplifying circuits must extendfrom a horizontal antenna to its ,orr .e,-spondin;r transmitting antennalocated in vtlieolher group, `which may be some distance array.Theamplifying circuit itself comprises plia shifting devices, bundfilters and amplifie similar to those described in connection with theprevious figures. In a radio relay el' this type, received signals setup currents in the horizontal antenna which are transmitted through thephase shifting device PSL, the filter F1 and the levi power ainpliiierA1, thence through the power amplifier A2, the filter F2 and the phaseshifting device PS2, tothe transmitting 'antenna X1. Although receptionand transmission are effected upon the saine frequency singing ispreventedthrough the balanced relationship of the same frequencies asX2.

horizontal antenna tothe vertical antenna.Y

By proper spacing of the antennae and byV proper control of theamplitude and phase of the currents applied to the individual antenna ofthe array, radio signals may be re` layed and the direction oftransmission may be controlled.

The arrangement shown in Fig.` et, While operating upon the principle oftransmis-` sion and reception of signals upon the same frequency, isdesigned for the simultaneous transmission of tvvo channels either inthe same or in opposite direct-ions.V The `antenna structure is of *thebalanced type shown in Fig. 8, With the exception that both the groundantenna and the vertical antenna have two degreees of freedom. theoperation of the arrangement shown in this figure, if a waverepresenting a band of frequencies such as fl-l s or )c1-18 strikes thehorizontal antenna, oscillations Within the band of frequencies will lbeset up in the horizontal antenna. The Vcurrent `Within this band offrequencies will be transmitted through the phase shifting device PS1and through the band filter F,l `to the amplifier A1, thence throughthepower amplifier A2 and the second band `filter F2, which is adapted topass the same range of frequencies as F2, and then throughthe phaseshifting device PS2 to the vertical antenna X, Which as stated, isadapted to oscillate at the Since the antenna X1 occupies such aposition With respect to the horizontal antenna X2 as not to createoscillations in X2 when Xlis radiating, relatively high amplication canbe obtained without producing singing of the repeater. In a similarmanner if a Wave representing a band of frequencies )i2-ts or f2-sstrikes the ground antenna X2, oscillations of the same band offrequencies will be set up in the said antenna. These oscillations willbe transmitted through the phase shift-ing device PS3 and the bandvfilter F which is designed to transmit Athe range of frequenciesrepresented by f2-te or f2'm a; Thecur- .rent Within this band offrequencies `will` be amplified by the loW power amplifier A.L and alsoby the high power amplifier A2, and vthe resultant amplified currentWill be trans mitted through the band filter F4 and then through thephase shifting device PSd to the antenna X1 which will oscillate at thetransmitted frequencies. Although the amplitiers A, and A2 arerepresented as being common to the paths of the tivo channels, it is, ofcourse, apparent that separate amplifiers of both types individual tothe paths of the tivo channels could be used.

The arrangement'shown in Fig. 4 constitutes only a single unit of aradio repeating system, but it is to be understood that there will be aplurality of such units constituting a repeating station in which theadthe manner. described in connection with Fig. 3, and the transmittingantennae Will be similarly spaced. By properly controlling the phase andthe amplitude of the received and transmitted current on each'unitcircuit of an array, the direction of transmission and reception may bereadilycontrolled.

Fig. 5 shows a unit circuit of a repeating station characterized byseparate receiving and transmitting antennae, the receiving antennabeing of the loop type and the transmitting antenna being vertical.Oscillations of the frequency f, +S or f2-s received by the loop antennaX2 will be transmitted through the amplifier A1 and the phase shiftingdevice PSL and the band filter F, to the power amplifier A2 connectedwith the trans mitting antenna X,. Since the radiation and receptioncharacteristic of a loop antenna is, as shown in F ig.V 5, such that themaximum eiiiciency is along a line coinciding with the plane of the loopand the minimum c'liciency along the axis perpendicular to the loop,interference from the oscillations transmitted by antennae as X1 can besubstantially` prevented by adjusting thephase shifting device PS1 sothat the transmitting antenna Will have a characteristic for example,slich `as is shovvn in Fig. 4 `with the major axis of the characteristicperpendicular tothe plane of the receiving loop. Accordinglyinterference may be substantially prevented even though the two antennaeare responsive to the same frequencies. The arrangement shown in Fig. 5constitutes but a single unit of the radiating system and it to beunderstood that there will be a plurat ity of antennsearranged inankarray with suitable local. circuits individual to each pail' ofreceiving and transmitting antenua..

` Figs. 6 and 61" are modifications of the form shown "in Fig. 5, themodification consisting in arranging a structure for the s multaneousreception and tansmissimi of two channels. Thus the `loop X2 is responsive to carrier frequency f', and the loop X/ is responsive to thecarrier frequency f2. In Fig. 6a a single loop.k having two degrees offreedom such as the frequencies f, and f2 takes the place of thetwoloops iu Fig.` 6. The t 'ansmission of currents at these frequenciesthrough the local circuits to the transmitting antenna X, is similar tothat described in comiection with Fig. The circuit arrangements shown inFigs. f3 and 6a are units of a radio repeater sr tem ,and there Wouldbe, of course, a plurality roo the directional characteristic shown inFig. t,

Fig. 7 is a variation of the idea embodied in Fig. 5. The repeatercircuit illustrated by F ig. 7, which represents one unit of a directiverepeating station, is intended for: the transmission of amplifiedsignals having the same frequency as the received signals. The circu-itcontains a receivingr loop X2 for receiving oscillations of th frequency7' which are amplified. by the low power amplifiers A, and A. andimpressed upon the band filter F,. Current of the frequenciestransmitted through the band lter F1 will be amplified by the poweran'iplilier A: and impressed upon the transmitting antenna X1. Freedomfrom interference from the transmitted oscilla tions obtained partly byproper orientation of the loop antenna and partly by feedingl from thetransmitting antenna to the circuit of the loop antenna a certainani-.cunt of current, the phase of which as applied to the loop circuit`is controlled by the phase shifting device PS1. The phase angle of thistransmitted current. which may be termed the neutralizing current, whenapplied to the loop circuit is suchv as to neutralize currents set up inthe said loop as the result of direct radiation from the ltransmittingantenna thereto. The arrangement shown in Fig. 7 represents but a singleunit of an array, and there would, of course, be a plurality of antennaesuitably spaced and having a local connecting circuit individual to eachpair of receiving and transmitting antennze.

Fig. 8 represents a complete ,system comprising two terminal stations Aand B, and a repeater station vC intermediate the said terminalstations. The repeater station comprises an array of transmittingantennte X X2 and XM and also an array of receiving antennaerepresented' as loops and X1 X2 and X3. Each pair of transmitting andreceiving antennze is connected by a local circuit, such for example, asthat shown connecting the antennae X2 and X2 containing a low poweramplifier AU a phase shift ing device PS a band filter F, and a powcramplifier AT At each of the terminal stations a low frequency signalingcircuit L, is connected with the terminal circuit by means of a triplewinding transformer T, which hasl associated therewith a network N,designed to balance the line LV The input side of the terminal circuitcomprises a receiving loop X] an amplifier A3, a detector Dl and asecond amplifier Ay The output branch of the said terminal circuitcomprises an amplifier A5, a modulator Ml and an oscillator O, which isconnected with the transmitting antennae X1. The apparatus constitutingthe terminal station B is similar to that at terminal station A andneeds no further explanation. Low frequency signals arrivin over theline L1 will be impressed by t 1e transformer T1 upon the .output branchl of the terminal station A. These low frequency signals will beamplified by the amplifier AG and willmodulate y in the modulator M,`the high frequency oscillations set up by the oscillator O1. Themodulated oscillations ,when radiated by :the directive array of whichantennae X1 is a part will be received by the loop antennai X1', X2, andX3 constituting partfof an array of the repeatingstation C, which aretuned for the reception of oscillations ofthe frequency transmitted bythe power oscillator O1. These received oscillations willbe amplified bythe amplifier' A1 and ,the currentin each local circuit will beVadjusted in phase by the phase shifting device PSL so asto retain theproper directional chai'- acteristic of the array. The current will betransmitted through the band filter F, land when amplified by the poweramplifier A2 will be transmitted by the transmitting antennae X X2 andXW Thev array of which the latter antennae form a partis designed todirect its energy toward vthe receiving loop X5 of the station B, whichis tuned for receiving oscillations of the frequency transmitted b therepeater station. plified by the amplifier A6 `detected by the detectorD2, and again amplified .by ,the amplifier A7. The resultant lowfrequency signals will be impressed .across the'low frequency signalingcircuit L2. In similar manner low frequency signals arriving over theline L2 will be transmitted from the station B by the transmittin'antennae These signals will be relaye by the repeating station() andimpresscdupon the terminal station A.

Fig. 9 shows a complete system which dilers from that disclosed in Fig.8 primarily for the reason that the carrier oscillations, generated atstation A, are transmitted together with the side bands to the repeatingstation@ where both the carrier and the side band frequencies areamplified and are then transmitted lto the terminal station B where thereceived carrier is used not only for the detection of the received sideband frequencies, but it also serves as `the carrier of signal frequencyfrom -station B to station A. At station C, X1 represents a transmittingzantenna of an array and Xl represents a receiving loop of an array. Alrepresents a low power amplifier and A2 a high power amplier'whoseoutput side is connected with a phase shifting device PS1, which iscoupled to the transmitting antenna X1. The receiving loop X, isdesigned to receive the carrier and side'band frequencies. The receivedcurrent will be amplified by the amplifier A..I and will be detected bythe detector. D1. The resultant The received oscil ations will be am`line L1 at the stationA will be impressed by the transformer T1 uponthe output circuit l. These currents will serveto moduv late the highfrequency oscillations setup by the oscillator O1- which operates f incon-` junction with the modulator -M1.` `The resultant vside bands ofoscillations, together with the carrier, 'will be radiated by theantenna X and will be received b the loop X1 at the relay station. Botht ye carrier and the side band frequencies will be am-` pliiied at therelay station and will be transmitted from the antenna `X1.g kDueto thedirective qualities of the array, ofwhich antenna X1 is a unit, theoscillations of the carrier and the side band frequencies will bereceived at the loop X5 located at station B. Currents of allfrequencies will be amplified by the amplifier A4, and the signalfrequency will be detected by the detector D2 and impressed upon theline L2. A part of the energ of thev carrier frequency will betransmitted7 to the branch circuit 2 and will be impressed upon thefilter F1, which is `designed to transmit the carrier frequency. Currentof the carrier frequency will pass through thelilter Fl and will bemodulated by the signal frequencies arriving over the line L2 fortransmission from the antenna] X5. It will be seen that the arrangementdisclosed in Fig. 9 is adapted for the repeating of messages in eachdirection using the same fre ueney for receiving and transmitting at t erepeating station. Although a particular form of repeating circuit isshown,`

it is to be understood that any forms shown in the preceding figures maybe used in the system shown in Fig. 9.

Fig. l0 shows the geographical distribution, for example, of fourrepeaters located between two terminal stations. Any form of the antennama be used for receiving and transmitting. It is necessary only that thedirection of reception and transmission shall be Vperpendicular to 'eachother so as to avoid singing of the repeaters.

This invention is broadly directed to the combination of repeatingcircuits with directive antenna arrays. From the foregoing descriptionsit will be seen that 'the ob- 'ects, set forth in the beginning, mayreadily e obtained by the means described and illustrated. Furthermore,yit should be clearly stated that the amplifying circuits are in realitytranslating circuits capable of modifying the current ina variety ofways apart from amplifying, such as frequency selection by filters andphase control by the phase shifting devices. It is also desirable tomake definite that the amplifiers may be either a single `stage ormulti-stage arrangeby the transformer T3v ment, and may be ofthethermionic vacuum tube or otherwell known type.

" It will, of course, be apparent that the invention is not .limited tothe particular forms and arrangements shown in the aforedescribedfigures, since it is capable ofemloodiment` in a variety of other anddifferent forms Within the spirit and scope of the appended claims.

What is claimed is: l l. In a radio repeating system the combinationwith an antenna array for the reception and transmission of signals, of`a plurality of amplifiers connected therewith, means to control thephase of the currents `applied tothe antennae of the said array, andmeans to control the phase of the cur-l rents received from thesaidantennee and applied to thesaid amplifiers.

2. In a radio repeating system the com- `bination with'- an antennaarray of a plurality Vof repeating circuits individual to jthe antennaeof the said array including frequenc selecting means, means to cont-rolthe p ase of the currehts` received by `the antennae of the said arrayand means to control the phase of the currents applied to the antennaeof the said array for transmission therefrom.

3. In a radio repeating system the combination `with an antenna arrayforthe reception and transmission of` signals of a plurality ofrepeating circuits each individual to an antenna of the said varray andeach having its input and its output circuits connected with itsrespective antenna, and means associated therewith to prevent singing ofthe said repeating circuits.

4. In a radio repeating-system the comblnation with an antenna array forthe reception and transmission of radiant energy of a plurality of localamplifier circuits each individual to and having its input and itsoutput ends connected with one antenna of the said array, the said localcircuits having associated therewith devices for controlling the phaseof the received and the transmitted energy.

5, In a radio repeating system the combination with a repeating stationcomprising a directive antenna arra having amplifiers associatedtherewith or the amplification of signals transmitted thereto of aplurality of terminal circuits adapted to work in conjunction with thesaid repeating circuit, one of said terminal circuits having a source ofcarrier oscillations, and having its antennae tuned to transmit carrieroscillations to the second terminal circuit` to be used therein for thepurpose of detecting received signals, the said second terminalstationhaving means to utilize a portion of the said carrieroscillations as the carrier of signals to the said first terminalstation.

6. In a radio repeating system the coml UU bination with an antennaarray comprising a plurality of antennae each for the reception .andtransmission of signals, of a plurality `and mear-,1s t0 ,Control thephase 0f the Output current.

8. In a radio repeating system, the combination with an antenna arraycomprising a plurality of antennzeJ each for the reception andtransmission of signals, of a plurality of translating circuits, eachhaving its inputend and its output end conjugately connected with one ofsaid antennae whereby singingof each of said circuits is prevented, andeach 0f said Circuits haring an amplifier, means to control the phase ofthe current applied to the said amplifier, and means to control thephase of the current applied by the saidainpliiier to its antenna.

9. In a radio repeating system, the combination With an antenna arraycomprising a plurality of antennae each for the reception andtransmission of signals, of a plurality of translating circuits, eachhavlng its input end and its output end conjugately connected with oneof said antennae whereby Vsinging of each of said circuitsis prevented,

cluding one of saidl amplifiers to connect the iii-ppi side andthe.Output side .of ,its amplfier with the antenna with which the4 saidamplifier ,is intend ip cooperate 11- In a .radio repeating system, the,6,0mbinationv with a plurality of consiiiuiing an array for thetransmission spd reception 0f signals, 0f s plurality 0f amplifiershaving input and. ppfpili Cifsuts, each cooperating with one of the saidantennae, a plurality of coupling means each connested with Qns 0f saidantenas@ spd also with the said input and Ontpnl circuits of theamplifier @Oppsfptng wif3 .the same antenna, the said coupling meansbeing so designed and the connections being so effectedY that theoutputYcurrents produce no effect upon the input circuit and likewise theinput current no effect uponl the output circuit. i

In testimony whereof, we have signed Our names t0 this spifiltpp this27th dei of December, 1921. t

LLLQYD EsBENscHiED- DE Loss K. MARTJIN.

